Information about a known recording and/or reproducing apparatus as defined in the opening part of claim 1 and information about a cassette with a magnetic tape as record carrier tape for such a recording and/or reproducing apparatus is obtainable via the internet, namely at the internet address xe2x80x9cwww.lto-technology.comxe2x80x9d. In connection with the known recording and/or reproducing apparatus and the known cassette reference may also be made to the two patent documents WO 98/44506 A2 and WO 98/44499 A1.
The invention relates to a recording and/or reproducing apparatus as defined in the opening part of claim 1.
Information about a known recording and/or reproducing apparatus as defined in the opening part of claim 1 and information about a cassette with a magnetic tape as record carrier tape for such a recording and/or reproducing apparatus is obtainable via the internet, namely at the internet address xe2x80x9cwww.lto-technology.comxe2x80x9d. In connection with the known recording and/or reproducing apparatus and the known cassette reference may also be made to the two patent documents WO 98/44506 A2 and WO 98/44499 A1.
In a known recording and/or reproducing apparatus, whose reel drive device 35 is shown in sectional view in FIG. 11, a sleeve B is press-fitted onto the drive shaft 46A in the area of one end of the drive shaft 46A, which sleeve B has two circumferential recesses C and D, the third magnetic circuit element 50 being accommodated in the area of the recess C situated nearer the free end of the drive shaft 46A and having a clearance with respect to the recess C of the sleeve B and a ring-shaped portion E of the plastic drive member x formed by insert-molding of the sleeve B and the third magnetic circuit element 50 being accommodated in the second recess D, which precludes a relative axial movement between the drive member 47 and the sleeve B and, consequently, the drive shaft 46A, because of the force fit (press fit) between the sleeve B and the drive shaft 46A. In this construction the third magnetic circuit element 50 is formed by a comparatively thin steel disc 50 having a thickness of approximately 1.0 mm, which is made by a punching operation and serves as a magnetic return path. An annular magnet 49 forming a second magnetic circuit element 49 is connected to the comparatively thin steel disc, namely by means of an adhesive joint.
In the known recording and/or reproducing apparatus it has been found that as a result of the insert-molding of the comparatively thin steel disc 50 in a plastic in order to form the drive member 47 including its drive-member-side drive teeth 48 the comparatively thin steel disc 50 is subject to substantial mechanical loads owing to so-called shrinkage of the plastic, which gives rise to distortion and warping as well as an additional twisting of the steel disc 50. These deformations of the steel disc 50 result not only in the steel disc 50 having a non-perfect flat shape but also in the drive teeth 48 of the drive member 47 being subjected to such a strong deformation that this has an undesired and negative effect on the effective tooth height, which should be as constant as possible. Owing to the afore-mentioned deformation the drive-member-side drive teeth 48 are disposed at different axial levels, as a result of which these drive-member-side drive teeth 48 do not guarantee a satisfactorily uniform cooperation with the drive teeth of the reel toothing of a supply reel accommodated in a cassette. In operation of the known recording and/or reproducing apparatus a consequence of the varying axial height positions of the drive-member-side drive teeth 48 is that via the reel teeth and the supply reel the drive-member-side drive teeth 48, whose height position varies, exert a disturbing influence in the direction of the tape width on the magnetic tape unwound from or wound onto the supply reel, as a result of which variations occur in the height position of the magnetic tape, the frequency of said variations being dependent on, inter alia, the winding diameter. These variations in the height position can no longer be compensated by an actuator device carrying a magnetic head for scanning the tracks on the magnetic tape, as a result of which a correct recording and reproduction may be adversely affected or may even be impossible.
It is an object of the invention to preclude the afore-mentioned problems and to provide an improved recording and/or reproducing apparatus.
To achieve the afore-mentioned object, according to the invention, the characteristic features defined in the characterizing part of claim 1 are provided in a recording and/or reproducing apparatus as defined in the opening part of claim 1. Owing to the provision of the characteristic features in accordance with the invention it is achieved in a simple manner that as a result of the direct connection of the drive shaft to the third magnetic circuit element and as a result of the finish of the magnetic circuit element by a turning operation, which is preferably effected after the connection of the third magnetic circuit element to the drive shaft, the third magnetic circuit element is oriented exactly perpendicularly to the drive shaft and, owing to its dimensioning in accordance with the invention, has such a rigid and non-deformable construction that insert-molding of the third magnetic circuit element, in order to form the drive member including its drive-member-side drive teeth, cannot lead to any warping, twisting or deformation of the third magnetic circuit element and, consequently, of the drive teeth connected to the third magnetic circuit element. Thus, by means of the measures in accordance with the invention it is achieved that all the drive-member-side drive teeth are disposed at the same axial level with a high accuracy. This has the advantage that during cooperation of the drive-member-side drive teeth with reel teeth of a supply reel of a cassette no undesirable influences are exerted on the magnetic tape and, consequently, the height position of the magnetic tape is not adversely affected, as a result of which a correct recording and reproduction is not disturbed or impaired by causes attributable to the drive-member-side drive teeth or the reel drive device.
In a recording and/or reproducing apparatus in accordance with the invention it has proved to be very advantageous when, in addition, the measures defined in claims 2 to 8 are taken. Tests have shown that these measures are particularly advantageous, particularly in view of an optimum compromise between, on the one hand, the size, the stability and non-deformability of the drive member and, on the other hand, the required space and the required mass of the drive member.
The above-mentioned as well as further aspects of the invention will become apparent from the embodiments described hereinafter by way of example and will be elucidated with reference to these examples.
The invention will now be described in more detail with reference to the drawings, which show two embodiments given by way of example but to which the invention is not limited.